Suction head for vacuum cleaners



Se t. 14, 1954 G. P. PF'AFFLE ETAL SUCTION HEAD FOR VACUUM CLEANERS 5 Sheets-Sheet 1 Filed Aug. 24, 1948 INVENTORS GORG P. PFHFFLG;

wlLunM CLGLFIND Qttorne y \llilllnlll lh ll illv Z MJMEE Sept. 14, 1954 cs. P. PFAFFLE ET AL SUCTION HEAD FOR VACUUM CLEANERS 5 Sheets-Sheet 2 Filed Aug. 24, 1948 INVENTORS I PFHFFLE. WILLIAM CLGLHND P 1954 G. P. PFAFFLE ETAL 2,688,763

SUCTION HEAD FOR VACUUM CLEANERS Filed Aug. 24, 1948 5 Sheets-Sheet 3 FIG. 6 a; w 4

- FIG 7 INVENTORS GORGE.- P. PFHFFL Wl-LUHM CLGLRND BY Sept. 14, 1954 G. P. PFAFFLE ETAL suc'rrou HEAD FOR VACUUM CLEANERS 5 Sheets-Sheet 4 Filed Aug. 24, 1948 INVENTORS PFHFFLQ P 1954 G. P. PFAFFLE ETAL SUCTION HEAD FOR VACUUM CLEANERS Filed Aug. 24, 1948 5 Sheets-Sheet 5 INVENTORS GGORGG P. PFHFFLG,

WILLIQM CLELHND Patented Sept. 14, 1954 NT 7 OFFICE SUCTION HEAD FOR VACUUM CLEANERS George P. Pia-file, Akron, and William Cleland, Cuyahoga Falls, Ohio Application August 24%, 1948, Serial No. 45,824

1% Claims.

This invention relates to suction cleaners and in particular relates to a nozzle or head for suction cleaners.

In the past, so-called vacuum cleaners have generally used suction nozzles of substantially conventional type, wherein air is drawn into the mouth of the nozzle, inwardly from all directions, by vacuum means attached to the same, and hence they have been inefficient for picking up dirt, lint, etc., and objectionable because of the use of rotary beaters. Certain types of nozzles have been provided with spiral brushes or ribs for applying a beating action to rugs or carpets in conjunction with application of suction thereto. These heaters caused undue wear on carpets or the like. Moreover, such beater-type cleaners could not be operated on bare surfaces and cleaners having no heaters were substantially useless on bare floors.

One object of the present invention is to provide a nozzle or suction head for a vacuum sweeper, which will have maximum cleaning efficiency by providing uniform suction on the areas covered by the mouth of the nozzle, whether on a bare floor or a carpet or rug.

Another object of the invention is to provide a suction head of the character described which, in the case of small hand-type cleaners, will be very effective for cleaning fabric surfaces having a pile or nap, from which it is often difficult to remove dirt or lint.

Another object of the invention is to provide a suction head characterized by having self-adjusting surface-agitating means which is frictionally engageable with the surfaces to be cleaned, but which will not have the beating effect of known types of sweepers which have caused undue wear on rugs and carpets, for example.

Another object of the invention. is to provide a suction head of the character described having surface-agitating means of a type referred to in the last paragraph, but which is adapted to be used on bare floors as well as on carpets or rugs.

Other objects of the invention will be manifest from the following brief description and the accompanying drawings.

Of the accompanying drawings:

Fig. 1 is a top plan view of a sweeper head embodying the features of the invention;

Fig. 2 is a front elevation thereof;

Fig; 3 is a transverse, vertical cross-section taken substantially on the line 3-3 of Fig. 1;

Fig. 4 is a bottom plan view of the sweeper head illustrated in Figs. 1 to 3;

Fig. 5 is a cross-section taken substantially on the line 5-5 of Fig. 1;

Fig. 6 is a cross-section similar to Fig. 5, but illustrating the movable parts of the suction head in operative condition;

Fig. 7 is a cross-section taken substantially on the line 'l! of Fig. 1;

Fig. 8 is a cross-section taken substantially on the line 8-3 of Fig. 1;

Fig. 9 is a bottom plan view of a modified form of the invention, specifically illustrating a handtype vacuum cleaner;

Fig. 10 is a side elevation, partly broken away and in section of a hand-sweeper illustrated in Fig. 9;

Fig. 11 is across-section taken substantially on the line H-ll of Fig. 9;

Fig. 12 is an end view of the sweeper illustrated in Figs. 9 and 11, as viewed from the left of Fig. 10;

Fig. 13 is a cross-section similar to Fig. 1 1-, but illustrating movable parts on the sweeeper head in operative position;

Fig. 14 is a view similar to Fig. 10, on a reduced scale, illustrating the use of the handsweeper with an attachment thereon for cleaning Venetian blinds.

Referring particularly to Figs. 1 to 8 of the drawings, the numeral l5 designates a suction head or nozzle for a vacuum sweeper, the same comprising an elongated, generally rectangular casing of hard material, such as metal or synthetic resin. Front, back and opposite end walls l6, l1, l8 and 19, respectively, of the casing are rounded at the bottom edges thereof, as indicated at 20, 2|, 2-2 and 2-3, to provide a smooth continuous edge at the mouth of the suction head for smooth engagement with the surface to be cleaned, and at the same time providing a substantial air-seal with said surface for purposes to be described later.

The casing I 5 is formed with an opening therethrough being defined at the top by an elongated, rectangular rib portion 24 over which is received a complementally channel-shaped portion 2%: of a diaphragm member 26, which is generally in a horizontal plane parallel to said mouth edge of the casing, and closes the top of the opening i l and thereby forms with said walls IE to H an open-bottomed suction chamber 21. The diaphragm. member 26 is of vulcanized rubber or like resilient material, with the channel portion 25 formed for firm releasable engagement with the. rib portion 24', suffici'ent to retain the diaphragm member positioned as best shown in Figs. 3, 5, 6 and 7 in normal use of the suction head. A flexible wall or diaphragm 26a of the member 26 has as nearly as possible the area of the mouth of the nozzle, and is formed, as by vulcanization methods, of the rubber or like resilient material normally bulged upwardly as best shown in Figs. 3, and 'I. That is, the diaphragm 26a will be bulged upwardly (or outwardly) when the pressure within the suction chamber 2! is equal to the atmospheric pressure on the outwardly exposed upper side thereof, due to the inherent tendency of the rubber to resume normal molded shape.

At one end and along the back of the elongated casing I5 there is provided an integral enlargement IBa through which extends a passage |5b from the interior of the vacuum chamber 21 to the center of the casing at the rear thereof, said enlargement terminating in a rearwardly extending tubular portion 30 which may communicate with a separate suction-pump unit (not shown) through a flexible tube 30a. The suction pump means, however, may be mounted directly on the suction head, in which event a suitable hollow handle may be provided to extend angularly upwardly of the head. Suitably secured to the under side of the diaphragm 26a may be a plurality of elongated brush members or wiper elements 3|, 3|, the same being shown arranged across the mouth of the nozzle in zigzag formation, so that when suction is applied through the passage I51) and within the chamber 21, while the mouth of the casing is sealed by engagement with a surface to be cleaned, the pressure within the chamber is correspondingly reduced and the atmospheric pressure applied against the exposed upper face of the diaphragm 26a will flex or bulge the same downwardly to engage surface-wiping edge portions of the flexible brushes or elements 3| with said surface being cleaned (see Figure 6). The diaphragm preferably is formed fiat on the surface portions thereof to which the brushes 3| are attached, but in any event the brushes will conform to the surface to be cleaned whether flat or of somewhat irregular contour.

Because the mouth of the nozzle, as when in use for cleaning a carpet or rug, is substantially air-sealed a small air-inlet 33 is provided in the casing |5 at the top thereof and at the end opposite to the inwardly-opening end 32 of suction passage I519. The inlet 33 may be shaped substantially as shown to have a flexible, resilient extension 34 from the diaphragm channel 25 adapted to close the inlet, when the pressure within the chamber 21 is equal to or somewhat less than the atmospheric pressure, it being understood that when suction is applied to the chamber as described, air will be drawn through the inlet 32, past the resilient extension 34, and along a well-defined path sweeping from the air-inlet end of the suction head to the suction passage opening 32 at the opposite end thereof.

Suitable means may be provided for adjusting the resilient tension of the flexible valve means 34, to vary the effective size of the air-opening 33. As, for example, a screw 35 may be threaded through the end wall l8 of the casing and provided with a rounded inner extension 36 received in a correspondingly shaped recess formed in the valve 34.

In operation or use of the suction head l5, as for cleaning a carpet, it is utilized in the manner of known types of nozzles for vacuum sweepers.

Suction applied to the suction chamber 21 will, while the mouth of the nozzle is maintained sealed against the carpet, reduce the pressure within the chamber 21, thereby permitting atmospheric pressure to urge the diaphragm inwardly or downwardly and thereby to engage the flexible elements or brushes 3| with the carpet (see Figure 6). As the nozzle is drawn across the carpet the elements 3| are self-adjustingly urged into frictional engagement therewith, regardless of the type material previously operated upon or the depth of the pile or nap thereof, and will flex in opposite directions depending upon the direction in which the head is moved laterally as viewed in Figure 6. The amount of pressure applied to the carpet through the elements 3|, however, may be readily adjusted by turning the screw 35 in proper direction to vary the effective air-inlet opening past rubber valve 34.

The diaphragm member 26 is easily removable to be either replaced with a new diaphragm member or with another dipahragm member having a different type of agitating element or elements. As, for example, member 26 may be provided with relatively stiff agitator elements of shape and arrangement similar to elements 3| (Figures 3 to 7.

For cleaning certain materials having a fine pile or nap thereon, the member 2611 may be of non-flexible construction, integral with the casing l5, with the ribs either flexible or rigid and extending to approximately a plane across the mouth edges of the suction head, as in the shape and arrangement shown in Figures 12 and 13.

Figures 9 to 14 illustrate a modified form of the invention, specifically a small hand-type suction cleaner head adapted for use in cleaning the fabric material of furniture or the like. In this form of the invention the numeral 40 designates a one-piece casing, of vulcanized rubber or like resilient material, having a continuous perimetrical wall portion 4| and a top wall 42 defining a vacuum chamber 43 opening at the bottom of the casing. The wall portion 4| is gen erally egg-shaped and rounded at the mouth edge thereof for smooth engagement with the surface to be cleaned, as previously described, this wall portion 4| being relatively thick to be substantially self-supporting or inflexible as compared with the upper wall 42 which is relatively thin or of varying thickness to be substantially flexible from the line of juncture thereof with wall portion 4|. The flexible wall 42 constitutes a diaphragm, the same having a plurality of elongated rib portions 44, 44 integrally molded with respect thereto. In the normal molded condition of the casing 40 the diaphragm or upper wall portion 42 is substantially in a horizontal plane and adapted to be flexed or bulged inwardly by atmospheric pressure upon application of suction to the chamber 43, for urging the rib portion 44 toward agitating or frictional engagement with a surface to be cleaned.

To this end, for application of suction to the interior of the chamber 43 the enlarged end of the casing 4| is provided with a reduced extension 45 into which is fitted a conduit 46, which may be of relatively stiff material and adapted to extend to a separate unit for supplying vacuum means, preferably with the flexible conduit (not shown) intermediate the vacuum source and conduit 46. For the purpose of making the suction within the casing 4| effective for cleaning purposes, it being understood that the bottom edges of the Wall portion 41 substantially fully seals the vacuum chamber 43 when the head at is applied to a surface to be cleaned, there is provided a relatively small shallow groove 47 in the bottom edge of the wall portion 4| at the end thereof opposite the suction conduit orifice 46a.

Casing to, in addition to being relatively small in size to be snugly held in the hand. of a user thereof, may have elongated recessed portions 48 and 39 in the side edges of the same for reception of the fingers of said hand of the user. In addition, the conduit portion 45 may be spiral or circular in form, substantially as shown in Figures 9, 12 and 14 for reception therethrough of the arm of the user of the device. The combination of this support on the arm with the gripping action of the fingers in the recesses 43 and 49 makes it possible for the user to have a substantially effortless control over the device while it is being used. The circular supporting means 45 provides means whereby the suction head may be suspended on the arm while the operator or user has both hands free to perform other work.

As illustrated in Figure 14, the suction head last described above may have applied over the same a bag or sock 49a, of suitable open-weave fabric or other porous material, the bag being retained on the casing as by having a reduced neck portion 56} tied around the reduced portion 45 of the casing it. With bag 49a thus applied to the suc tion head it is adapted to be effectively used for cleaning surfaces of relatively small area, such as the slats of Venetian blinds.

In all forms of the invention shown and described above, the suction chamber is substan tially elongated and the air drawn into the charm her from one end to the other by reason, of the suction means following an elongated path corresponding to the elongated shape of the mouth of the suction head, whereby maximum efliciency of cleaning is attained by the devices disclosed. That is, the cleaning operation is concentrated on the areas immediately covered by the suction head as it is moved over such areas.

Because of the self adjusting nature of the agitating elements mounted on the flexible diaphragms of the suction cleaners described above, the cleaners may be moved from one type of surface to another including covered or bare surfaces.

Other modifications of the invention. may be resorted to without departing from the spirit thereof or the scope of the appended claims.

What is claimed is:

1, A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a generally self-supportingly rigid casing having walls defining a suction chamber opening at the bottom thereof, said bottom of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a flat surface to be cleaned substantialh completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said chamber, one wall of said chamber substantially superposing said bottom opening and being resiliently flexible and of substantially broad lateral area with outer and inner surfaces thereof exposed to the atmosphere an to suction applied within the chamber, respectively, and at least one wiper element mounted on the suction side of said flexible wall and having surface-wiping edge portions positioned to be engageable with said surface to be cleaned by inward. flexing of the flexible wall, said flexible wall. being inwardly flexed by application of atmospheric; pressure to said outer surface thereof upon applying suction within said chamber, said flexible wall comprising a diaphragm of elastic material, and means for detachably securing said diaphragm to said casing.

2. A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a casing having walls defining a suction chamber opening at the bottom. thereof, said bottom of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a flat surface to be cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said chamber, one wall of said chamber substantially superposing said bottom opening and being flexible and of substantially broad lateral area with outer and inner surfaces thereof exposed to the atmosphere and to suction applied within the chamber, respectively, and at least one Wiper element mounted on the suction side of said flexible wall and having surface-wiping edge portions positioned to be engageablewith said surface to be cleaned by inward flexing of the flexible wall, said flexible wall being inwardly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction within said chamber, adjustable, valve means being included for controlling the. flow of air through said air inlet means.

3. A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a casing having walls defining a suction chamber opening at the bottom thereof, said bottom of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a flat surface to be cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said chamber, one wall of said chamber substantially superposing said bottom opening and being flexible and of substantially broad lateral area with outer and inner surfaces thereof exposed to the atmosphere and to suction applied within the charmber, respectively, and at least one wiper element mounted on the suction side of said flexible wall and having surface-wiping edge portions positioned to be engageable with said surface to be cleaned by inward flexing of the flexible wall, said flexible wall being inwardly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction within said chamber, adjustable valve means being included at one end of said chamber for controlling the flow of air through said air inlet means, said suction means communicating with said chamber at the opposite end thereof.

l. A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a casing having walls defining a suction chamber opening at the bottom thereof, said bottom of the casing having a surface-engaging portion surrounding said opening adapted to be friotionally engageable with a flat surface to be cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said chamber, one wall of said chamber substantially superposing said bottom opening and being flexible and of substantially broad lateral area with outer and inner surfaces thereof exposed to the atmosphere and to suction applied Within the chamber, respectively, and at least one wiper element mounted on the suction side of said flexible wall and having surface-Wiping edge portions positioned to be engageable with said surface to be cleaned by inward flexing of the flexible wall, said flexible wall being inwardly flexed :by application of atmospheric pressure to said outer surface thereof upon applying suction within said chamber, said flexible wall comprising a diaphragm having releasably interengageable portions for detachably securing the diaphragm to the casing.

5. A suction head for a vacuum cleaner adapted to be connected to a source of suction,

comprising a casing having walls defining a suction chamber opening at the bottom thereof, said bottom of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a flat surface to be cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said chamber, one wall of said chamber substantially superposing said bottom opening and being flexible and of substantially broad lateral area with outer and inner surfaces thereof exposed to the atmosphere and to suction applied within the chamber, respectively, and at least one wiper element mounted on the suction side of said flexible wall and having surface-wiping edge portions positioned to be engageable with said surface to be cleaned by inward flexing of the flexible wall, said flexible Wall being inwardly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction within said chamher, said flexible wall comprising a diaphragm of elastic material, said casing and said diaphragm having releasably interengageable portions for detachably securing the diaphragm to the casing, said diaphragm having a flexible extension across said air inlet yieldingly tending to close the same against atmospheric pressure through the inlet into said chamber.

6. A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a casing having walls defining a suction chamber opening at the bottom thereof, said bottom of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a flat surface to be cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said chamber, one Wall of said chamber substantially superposing said bottom opening and being flexible and of substantially broad lateral area with outer and inner surfaces thereof exposed to the atmosphere and to suction applied within the chamber, respectively, and at least one wiper element mounted on the suction side of said flexible wall and having surface-wiping edge portions positioned to be engageable with said surface to be cleaned by inward flexing of the flexible wall, said flexible wall being inwar ly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction within said chamber, said flexible Wall comprising a diaphragm of elastic material, said casing and said diaphragm having releasably interengageable portions for detachably securing the diaphragm to the casing, said diaphragm having a flexible extension across said air inlet terminating in a free end portion yieldingly tending to close the inlet against atmospheric pressure but permitting 8 atmospheric air to pass through the inlet into said chamber, control means for adjusting the degree of resistance of said flexible free end portion to said atmospheric pressure.

7. A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a casing having walls defining a suction chamber having an opening at the bottom thereof, said casing walls including a relatively rigid perimetrical wall and an upper wall of flexible resilient material having marginal portions thereof anchoringly supported on upper portions of the perimetrical wall to be in substantially superposed relation to said bottom opening, the bottom of the perimetrical wall of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a flat surface to be cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said suction chamber and operable to admit air to said chamber when said bottom opening is in substantially sealed relation to said flat surface, said flexible wall being of substantially broad lateral area with outer and inner surfaces thereof adapted to be exposed to the atmosphere and to suction applied within the chamber, respectively, and at least one Wiper element mounted on the suction side of said flexible wall and having surface-wiping edge portions normally positioned to be spaced above a said surface to be cleaned, said flexible wall being inwardly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction Within said chamber and thereby to urge said edge portions of the wiper elements into yielding engagement with said surface to be cleaned.

8. A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a casing having walls defining a suction chamber having an opening at the bottom thereof, said casing walls including a perimetrical supporting wall and a flexible upper wall anchoringly supported by said supporting wall to be in substantially superposed relation to said bottom opening, the bottom of the perimetrical wall of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a fiat surface to be cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said suction chamber and operable to admit air to said chamber when said bottom opening is in substantially sealed relation to said flat surface, said flexible wall being of substantially broad lateral area with outer and inner surfaces thereof adapted to be exposed to the atmosphere and to suction applied within the chamber, respectively, and at least one wiper element mounted on the suction side of said flexible wall and having surface-wiping edge portions positioned to be engageable with said surface to be cleaned by inward flexing of the flexible wall from normal shape thereof, said flexible wall being inwardly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction within said chamber and therebyto urge said edge portions of the wiper elements into yielding engagement with said surface to be cleaned, said casing and flexible wall being integral and of elastic plastic material, said supporting wall of said casing being of requisite thickness and consistency to be relatively inelastic and therefore rigidly selfsupporting, and the flexible wall being relatively thin and adapted to resume said normal shape due to the inherent resiliency of the elastic material of the same.

9. A suction head for a vacuum cleaner adapted to be connected to a source of suction, comprising a. casing having Walls defining a suction chamber having an opening at the bottom thereof, said casing Walls including a perimetrical supporting wall and a flexible upper wall anchoringly supported by said supporting wall to be in substantially superposed relation to said bottom opening, the bottom of the perimetrical wall of the casing having a surface-engaging portion surrounding said opening adapted to be frictionally engageable with a flat surface tobe cleaned substantially completely to seal said bottom opening against said flat surface, air inlet means from the atmosphere to said suction chamber and operable to: admit air to said charnher when said bottom opening is in substantially sealed relation to said fiat surface, said flexible wall being of substantially broad lateral area with outer and inner surfaces thereof adapted to be exposed to the atmosphere and to suction applied within the chamber, respectively, and at least one wiper element mounted on the suction side of said flexible Wall and having surfacewiping edge portions positioned to be engageable with said surface to be cleaned by inward flexing of the flexible wall from normal shape thereof, said flexible wall being inwardly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction Within said chamber and thereby to urge said edge portions of the wiper element into yielding engagement with said surface to be cleaned, said casing and flexible wall being integral and of elastic plastic material, said supporting wall of said casing being of requisite thickness and consistency to be relatively inelastic and therefore rigidly self-supporting, and the flexible wall being relatively thin and adapted to resume said normal shape due to the inherent resiliency of the elastic material of the same, said casing approximating the size of the hand and having opposed finger-receiving members integrally formed on said rigidly self-supporting portion thereof.

10. A suction head for a vacuum cleaner adapted to be connected to a source of suction,

comprising a casing having walls defining a suction chamber having an opening at the bottom thereof, said casing walls including a relatively rigid perimetrical wall and an upper Wall of flexible material having marginal portions thereof anchoringly supported on upper portions of the perimetrical Wall to be in substantially superposed relation to said bottom opening, the surface-engaging portions on the bottom of said. casing including means for supporting the casing on a surface to be cleaned in substantially air-sealed relation, air inlet means on said casing and operable to admit air to said chamber when said bottom opening isin substantially sealed relation to said flat surface, said upper wall being of substantially air-impervious material and of substantially broad lateral area with outer and inner surfaces thereof exposed to the atmosphere and to the suction within the chamber, respectively, and at least one wiper element mounted on the suction side of said flexible Wall and having surface-wiping edge portions positioned to be engageable with said surface to be cleaned by inward flexing of the flexible Wall, said flexible wall being inwardly flexed by application of atmospheric pressure to said outer surface thereof upon applying suction within said chamber .and thereby to urge said edge portions of the wiper elements into yielding engagement with said surface to be cleaned.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 514,677 Furnas Feb. 13, 1894 514,678 Furnas Feb. 13, 1894 936,222 Dalzell Oct. 5, 1909 1,012,634 Guild Dec. 26, 1911 1,211,902 Warner Jan. 9, 1917 1,394,789 Prell Oct. 25, 1921 1,970,290 Ernzer Aug. 14, 1934 2,157,077 Kroenlein May 2, 1939 2,164,392 Ellis July 4, 1939 2,235,226 Lofgren Mar. 18, 1941 2,243,935 Williamson June 3, 1941 FOREIGN PATENTS Number Country Date 375 Great Britain of 1905 116,997 Austria Mar. 25, 1930 464,634 Germany Aug. 22, 1928 

